a) Field of the Invention
The present invention relates to apparatus and method for controlling a yaw rate of an automotive vehicle. The present invention especially relates to the apparatus and method for controlling the yaw rate of the automotive vehicle in which a neutral point offset correction is made in a case where a detected absolute value of a steering angular displacement of a steering angle sensor is incorrect.
b) Description of the Related Art
In general, it is indispensable for detecting a Steering angular displacement caused by a steering operation through a steering wheel of an automotive vehicle as far as a yaw rate control of the automotive vehicle is concerned.
Hence, the yaw rate control apparatus is usually provided with a steering angle sensor which detects an absolute steering angular displacement with respect to a neutral steered position at which the vehicle runs straightly.
It is often the case where the detected value of the steering angular displacement by means of the steering angle sensor does not accurately correspond to the absolute steering angular displacement with respect to the neutral steered position at which the vehicle runs straightly due to an assembly error of the steering angle sensor when assembled onto a steering system of the vehicle, due to different steering angle sensors having different characteristics, and/or due to an environmental temperature variation.
In this case, the yaw rate control becomes inaccurate and the vehicle motion becomes unstable.
A Japanese Patent Application First Publication No. Heisei 3-61173 published on Mar. 15, 1991 exemplifies a previously proposed neutral point correction technique in which an estimated value of a neutral steering angle is calculated when the detected absolute value of the steering angular displacement is within a predetermined range over a running distance of the vehicle equal to or more than a preset running distance and this calculation condition becomes more strict than an initial calculation condition so that an accuracy of estimating the neutral steering angle can be improved.